We experimentally control the spectral structure of photon pairs created via spontaneous four-wave mixing in microstructured fibers. By fabricating fibers with designed dispersion, one can manipulate the photons' wavelengths, joint spectrum, and, thus, entanglement. As an example, we produce photon-pairs with no spectral correlations, allowing direct heralding of single photons in pure-state wave packets without filtering. We achieve an experimental purity of 85.9±1.6, while theoretical analysis and preliminary tests suggest 94.5% purity is possible with a much longer fiber.
@article{arxiv.0809.0071,
title = {Tailored photon-pair generation in optical fibers},
author = {Offir Cohen and Jeff S. Lundeen and Brian J. Smith and Graciana Puentes and Peter J. Mosley and Ian A. Walmsley},
journal= {arXiv preprint arXiv:0809.0071},
year = {2009}
}